The effects of heavy metal on the production of belite-rich cement using inorganic wastes

• Main Authors: Yi-Hung Wu, 吳怡虹
• Other Authors: Juu-En Chang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/07373156942838593458

碩士 === 國立成功大學 === 環境工程學系碩博士班 === 97 === To reduce the consumption of raw materials and energy in the cement industry, finding the alternative raw materials and reducing the sintering temperature are important issues at the moment. In this study, the potential cement materials such as oyster shell, rice husk, water treatment plant sludge, and Basic Oxygen Furnace slag are utilized as cement raw materials. Cement chemical parameters were controlled and electroplating sludge was added as a source of ion to stabilize the β-C2S thus produces belite-rich cement (BRC). Finally, to verify the feasibility of BRC in the engineering application, the pastes are mixed in different proportions to BRC and ordinary Portland cement (OPC) and undergo the test of hydration characteristics. The results show that the largest amount of C2S phase in the clinker is about 75 wt.%, when the chemical parameters of raw material settings are LSF = 0.75, SR = 4. But some of γ-C2S still remains inactive with water. Factor experimental design was used to exam the role of heavy metals on β-C2S stabilization, and the effect of Cr2O3 was found to be the most significant, and followed by NiO. For factors interaction assessment, addition of CuO and ZnO as well as Cr2O3 and ZnO are also considered as significant factors. In addition, the research of utilizing electroplating sludge as a part of raw materials confirms that the heavy metals in electroplating sludge have a stabilizing effect on β-C2S. When compared to the clinker without electroplating sludge addition; as the addition amount reaches 14 wt.%, amount of γ-C2S reduces from 7.8 wt.% to 0.3 wt.%, and amount of β-C2S increases from 63.4 wt.% to 77.6 wt.%, which effectively raised the hydration product activity of the clinker. In the hydration characteristics test, when BRC-to-OPC ratio (B/O) is less than 4 / 6, the compressive strength of pastes are in compliance with the standard of type I cement of CNS. In addition, the compressive strength of pastes has improved significantly after 7 days, and it is also greater than the standard of type IV cement of CNS at 28 days when the BRC-to-OPC ratio is 8 / 2. With the crystal phase rise and fall, it can be confirmed that the hydration of the clinker is ongoing and the hydration products are generated. Obtained from the microstructure, the hydration products in cements are Ca(OH)2, ettringite (AFt), monosulphoaluminate (AFm) and CSH gel.